WASHINGTON (AP) -- Men in China have the lowest rate of prostate cancer in the world, and a diet rich in garlic, shallots and onions may be one of the reasons.

Researchers at the National Cancer Institute report in a new study that a diet with lots of vegetables from the allium food group - which includes garlic, shallots and onions - reduces the risk of prostate cancer by about half. And the common Chinese diet includes hearty servings of these vegetables.

The study, appearing this week in the Journal of the National Cancer Institute, is based on interviews with 238 men with prostate cancer and 471 men who were free of the disease.

Men in the study, all residents of Shanghai, China, were asked how frequently they ate 122 food items.

The results showed that those who ate more than a third of an ounce a day from the allium food group were about 50 percent less likely to have prostate cancer than those who ate less of the foods.

"We checked on many food items and the allium food group stood out (as protective against prostate cancer)," said Ann W. Hsing, an NCI epidemiologist and the first author of the study. "But the conclusions need to be replicated in another study." She said the study was conducted in Shanghai because China has the lowest rate of prostate cancer in the world.

Scallions seemed to be the most protective. According to the study, men who ate about a tenth of an ounce or more a day of scallions reduced their prostate cancer risk by about 70 percent. For garlic consumption of the same amount, the prostate cancer risk was reduced by about 53 percent.

Hsing said that the typical Chinese diet is much more heavily seasoned with garlic, scallions and onions than is the traditional American diet. But even so, the amount of allium vegetables consumed is measured only in fractional ounces. For instance, the study suggests that an effective level of prostate cancer protection can be achieved with about one clove of garlic a day.

"The reduced risk of prostate cancer associated with allium vegetables was independent of body size, intake of other foods and total calorie intake," the study authors reported.

Hsing said the study reinforces earlier studies that have linked high vegetable consumption to a reduced risk of prostate cancer. For instance, earlier studies have found that that eating tomatoes and tomato products can lower risk of prostate cancer. Italy, where tomato sauce and garlic are favorites, has one of the lowest rates of prostate cancer in Europe, said Hsing.

Janet Stanford, a cancer epidemiologist at the Fred Hutchinson Cancer Research Center in Seattle, said the study by Hsing and her co-authors continues to support the general finding that "eating vegetables is a good thing."

Stanford said her group, in an earlier study, linked broccoli, cauliflower and related vegetables to a reduced prostate cancer risk, while a high fat diet increased the risk.

"This shows that your mother was right," said Stanford. "Eat more vegetables."

The Shanghai study was conducted by researchers at the National Cancer Institute, one of the National Institutes of Health, and at the Shanghai Cancer Institute in China.

Copyright 2002 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.